@bieling: "Apple IIe: Video Signal "NTSC-Compatible", Not "NTSC-Compliant"
I bought Sharp XA305 video recorders to record the video from my Apple
IIe systems: however, I am able to record only black and white pictures.
I tried the same setup with an older Sears model VCR and it worked
perfectly. I tried a new camcorder and got only black and white pictures
again. Sharp told me that this is because the Apple IIe has a
substandard NTSC signal.
Can you help?
The composite video signal coming from the Apple IIe is not stated to be
an NTSC-compliant signal. The signal coming from the video-out port is
only considered NTSC-compatible video. "Compatible" means that generally
the Apple IIe video will work with an NTSC device, although it may not
work in all situations. Specifically, the Apple IIe video signal should
work with all NTSC display devices.
When the Apple II was first designed, economy was of great importance.
The video circuitry was built with as few parts as possible. In the
design process, it was discovered that certain portions of the NTSC
broadcast specification could be omitted, yet still display a color
image on a standard television set. The one element that affects the
described situation is color burst. The Apple IIe does not contain the
color burst element of the NTSC video signal. By modulating other
portions of the video signal, the Apple IIe simulates this missing
information and allows an image to be produced on a television. To
provide a consistent color video image for video tape, this color burst
needs to be present.
In summary, the Apple IIe composite video signal was designed for
display proposes, not for videotaping purposes. The Apple IIe composite
signal is close to the NTSC specification and allows the video signal to
be displayed on television screens. This, however, does not indicate
that the signal can be recorded. Since the signal is similar to the full
NTSC specification, video sometimes records properly on videotape with
certain VCRs. In other environments, the signal may not oerickson@example.org.
The capability to record a monochrome image falls between these
extremes.
To have a true NTSC signal designed for videotaping, the Video Overlay
Card is required.
Article ID: 5508"
    @dakidd: "<snip>
<quote>
Why can't it? It's absolute fact. And based on the tag at the end, it 
looks like it might even be "directly from the mouth of Apple Inc."
You say 'toemaytoe', I say 'tuhmahtoh', that guy over there says 
'tuhmayter', and the gal across the hall says "termaytuh"- Everybody's 
talking about the same, usually more-or-less round, frequently red 
veggie that gets turned into ketchup (or catsup, if you prefer) paste, 
and/or spaghetti sauce, just saying it different.
Same thing with the Apple video signal and the NTSC standard - NTSC 
specifies "toemaytoe", but Apple video says "tuhmayter".
Whether any particular NTSC device understands or not depends on whether 
that device is "a snob" (Expects, and will only respond to, the perfect 
"Toe-mah-toe" pronunciation) or if it's a "Regular Joe" that hears 
anything from "toe-may-toe" to "termater" and goes "Oh, you want a 
tomato!" and hands you one
Most devices are "Regular Joes", but particularly when you start messing 
around in the high-end gear, you're real likely to find "snobs" crawling 
out of the woodwork and starting to sing about the rain in spain falling 
mainly on the plain.
By jorge, I think he's got it! :) 
Sorry, just couldn't resist a little "My Fair Lady" word-play in this 
one, since it's so appropriate :)
Don Bruder - <email_address> - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <<url> for more info"
    @mjmahon: "<quote>
Right.  There were some very expensive genlock cards made in the
late 1970's that put the Apple video on standard NTSC-standard
sync and timing specs.  The much less expensive Video Overlay Card
will also do this, if you really need it.
This is not so.  In all graphics modes, a color burst is present
(though it may not of "perfect" position or duration).  Almost
every NTSC device is *extraordinarily* sensitive to this color
burst, which is gated and used to phase lock a crystal oscillator
for chroma decoding.
In fact, there was an early change to the Apple II circuit to provide
more isolation when the color burst was switched off (in text mode)
so that TV monitors wouldn't pick up the tiny leak-through burst and
go into color mode!
As Don points out, only a *very* picky video processing system would
fail to lock to the Apple color burst.
That's a very conservative statement.  Most VHS video recorders will
record the Apple video signal just finethere were several applications
for titling videotapes that depended on it.
As the generation of spec-perfect NTSC timing and sync has become a
piece of cake (or a tiny sliver of silicon), the sloppy NTSC of the
early days has become rarer, so modern equipment is likely to be more
dependent on precise timing.
-michael
Music synthesis for 8-bit Apple II's!
Home page:  <url>
"The wastebasket is our most important design
tooland it is seriously underused.""
    @bieling: "<quote>
Sure, it comes from :
<<url>
What I think is that in the article, the two phrases that explain why
some recorders may not work are *not* true at all :
1.- "The Apple IIe does not contain the color burst element of the NTSC
video signal"
and
2.- "By modulating other portions of the video signal, the Apple IIe
simulates this missing information and allows an image to be produced on
a television"
Jorge Chamorro Bieling"
    @dakidd: "<quote>
For 50 GeekPointz(TM), what's that chunk of code supposed to accomplish? 
(not just the routine fragment of the rroutine that's visible, but the 
entire piece of code)
Answer below - no fair PEEK()ing! :)
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The part that's visible is the beginning of the ProDOS "/RAM" ramdisk 
driver code.
Don Bruder - <email_address> - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <<url> for more info"
    @dakidd: "<quote>
Why would that be untrue? All it takes to make color from a B&W signal 
is the proper "jiggling" of the signal timing. Nudge it a little in 
either direction, and you've got color dots rather than B&W dots. No 
need to "build" the NTSC colorburst part of the signal, and it ends up 
working with any hardware that isn't super-picky. Granted, it might come 
out looking like crap, like when you try to put 80-column text on a TV, 
but it at least worked to some extent in most cases.
Nowdays, rather than being surprised that a piece of gear chokes on the 
Apple II's "bastard NTSC" signal, I'd be more shocked to find gear that 
*DOESN'T* barf - The display gear these days is built to a lot tighter 
tolerances than "back in the day" to deal with all the new 
digital/hi-definition/S-video/etc. signals that all our digital gear is 
shipping to them for display. Back in the day, there was enough "slop" 
in the display hardware that tricks like the Apple II used were barely 
considered "tricks" at all unless you were the guy designing it.
Don Bruder - <email_address> - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <<url> for more info"
    @bieling: "<quote>
Because you need to have a reference to lock to. 
And the reference is the color burst. 
If the color burst is missing, it's like saying to the monitor : 
"this image comes in black and white".
This is so because of the way color information was added on top to the
NTSC black and white standard, so as to remain compatible.
The color burst is "the key" that turns on the color circuitry in a
tv/monitor.
no color burst=black and white."
    @mjmahon: "<quote>
No, you have to supply the color reference burst, or nothing in the
video signal can be interpreted as color.  (In fact, the presence of
the burst is the "flag" that color is being sent.)
You are confusing the absence of a distinct chroma subcarrier ("artifact 
color") with the absence of the color burst, an 8-10 cycle burst of
3.58MHz on the back porch of horizontal blanking that supplies the
reference frequency and phase for interpreting the chroma component
of the composite video signal.
It is apparent that the author of the original Apple article had the
same confusion.
In Apple video, the burst is supplied when color graphics are displayed,
but the chroma subcarrier is "simulated" by switching the video between
0 and 1 at rates that produce 3.58MHz components in the video signal
at amplitudes and phases (relative to the burst) that correspond to the
"Apple colors".
Agreed.  Sweep circuits could sync (and were adjustable) over fairly
wide ranges, and, as long as the burst frequency was *very* close to
3.579545MHz (so that the crystal-stabilized PLL could lock to it),
you were golden.
As video equipment goes digital, this tolerance is not part of the spec
and is being lost.
-michael
Music synthesis for 8-bit Apple II's!
Home page:  <url>
"The wastebasket is our most important design
tooland it is seriously underused.""
    @mjmahon: "<quote>
And I'm pretty sure that the exact duration or position of the Apple
color burst is not the real problemI suspect it is the slight
departures from standard scan frequencies/durations, as Scott reported.
In fact, that's what *makes* it a monochrome signal.  ;-)
Or anyone who understood the Apple II video signalthere were plenty
of them at Apple, so this must not have been widely proofread.  ;-)
-michael
Music synthesis for 8-bit Apple II's!
Home page:  <url>
"The wastebasket is our most important design
tooland it is seriously underused.""
    @bieling: "<quote>
It depends. 
If the problem is lack of color, then the culprit is more likely color
burst related. 
If it doesn't lock to it, then the problem is more likely related to the
timing or to the "custom" shape of the Apple II vertical
sync/equalizing/serration pulses during vertical blanking. 
Macrovision did a fortune with this..."
    @mjmahon: "<quote>
Maybe...but recovery of the burst requires prior phase lock to
the horizontal sync, so things are a bit intertwingled.
I do agree that if the burst frequency is off by much, you won't
get any color, but the Apple burst frequency is right on, unless
the 14.31818MHz crystal has drifted with age (which they do).
I have an Apple ][+ that has drifted enough that it no longer
produces color images on an analog monitor!  (I really should
get around to replacing that crystal...)
They sure didbut they inserted some big *very white* pulses in
the vertical blanking interval, and didn't fiddle with the timing
of what was already there.
-michael
Music synthesis for 8-bit Apple II's!
Home page:  <url>
"The wastebasket is our most important design
tooland it is seriously underused.""
    @bieling: "<quote>
The point is, as Macrovision knows, vcrs can be fooled by the shape of
the vertical blanking interval. And as the Apple II is somewhat
particular in this sense, I believe there's a chance that a certain vcr
dislikes the non-standard shape of this part the Apple II video signal.
In fact, iirc, Apple modified exactly this part of the video signal
several times during the life of the Apple II line. 
This may be a reason ?"
    @dakidd: "<quote>
Nah, can't do that... We'd be offending certain persons in East Elbonia 
(Lycopersicon happens to be a potent insult in certain dialects of East 
Elbonian, y'see) and we wouldn't want that happening now, would we? :)
Don Bruder - <email_address> - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <<url> for more info"
    @noone: "<quote>
... <snip>
Actually when I want a real NTSC video signal, I pump the IIe through my 
VCR and let it blur the digital dignal into a color one.  :)
Thankx,
Ed"
    @mjmahon: "<quote>
That works quite well, and often standardizes the sync in the process.
-michael
Music synthesis for 8-bit Apple II's!
Home page:  <url>
"The wastebasket is our most important design
tooland it is seriously underused.""
    @lyleREMOVE: "<quote>
People eat peas in the pod... the peas are seeds.
People eat green beans... the beans are seeds.
Lyle Syverson"
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